Class ValueExpressionImpl
- java.lang.Object
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- javax.el.Expression
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- javax.el.ValueExpression
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- com.sun.el.ValueExpressionImpl
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- All Implemented Interfaces:
java.io.Externalizable
,java.io.Serializable
public final class ValueExpressionImpl extends ValueExpression implements java.io.Externalizable
AnExpression
that can get or set a value.In previous incarnations of this API, expressions could only be read.
ValueExpression
objects can now be used both to retrieve a value and to set a value. Expressions that can have a value set on them are referred to as l-value expressions. Those that cannot are referred to as r-value expressions. Not all r-value expressions can be used as l-value expressions (e.g."${1+1}"
or"${firstName} ${lastName}"
). See the EL Specification for details. Expressions that cannot be used as l-values must always returntrue
fromisReadOnly()
.The
ExpressionFactory.createValueExpression(javax.el.ELContext, java.lang.String, java.lang.Class<?>)
method can be used to parse an expression string and return a concrete instance ofValueExpression
that encapsulates the parsed expression. TheFunctionMapper
is used at parse time, not evaluation time, so one is not needed to evaluate an expression using this class. However, theELContext
is needed at evaluation time.The
getValue(javax.el.ELContext)
,setValue(javax.el.ELContext, java.lang.Object)
,isReadOnly(javax.el.ELContext)
andgetType(javax.el.ELContext)
methods will evaluate the expression each time they are called. TheELResolver
in theELContext
is used to resolve the top-level variables and to determine the behavior of the.
and[]
operators. For any of the four methods, theELResolver.getValue(javax.el.ELContext, java.lang.Object, java.lang.Object)
method is used to resolve all properties up to but excluding the last one. This provides thebase
object. At the last resolution, theValueExpression
will call the correspondingELResolver.getValue(javax.el.ELContext, java.lang.Object, java.lang.Object)
,ELResolver.setValue(javax.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)
,ELResolver.isReadOnly(javax.el.ELContext, java.lang.Object, java.lang.Object)
orELResolver.getType(javax.el.ELContext, java.lang.Object, java.lang.Object)
method, depending on which was called on theValueExpression
.See the notes about comparison, serialization and immutability in the
Expression
javadocs.- Version:
- $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: dochez $
- See Also:
ELResolver
,Expression
,ExpressionFactory
,ValueExpression
, Serialized Form
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Field Summary
Fields Modifier and Type Field Description private java.lang.Class
expectedType
private java.lang.String
expr
private FunctionMapper
fnMapper
private Node
node
private VariableMapper
varMapper
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Constructor Summary
Constructors Constructor Description ValueExpressionImpl()
ValueExpressionImpl(java.lang.String expr, Node node, FunctionMapper fnMapper, VariableMapper varMapper, java.lang.Class expectedType)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
equals(java.lang.Object obj)
Determines whether the specified object is equal to thisExpression
.java.lang.Class
getExpectedType()
Returns the type the result of the expression will be coerced to after evaluation.java.lang.String
getExpressionString()
Returns the type the result of the expression will be coerced to after evaluation.private Node
getNode()
java.lang.Class
getType(ELContext context)
Evaluates the expression relative to the provided context, and returns the most general type that is acceptable for an object to be passed as thevalue
parameter in a future call to theValueExpression.setValue(javax.el.ELContext, java.lang.Object)
method.java.lang.Object
getValue(ELContext context)
Evaluates the expression relative to the provided context, and returns the resulting value.ValueReference
getValueReference(ELContext context)
Returns aValueReference
for this expression instance.int
hashCode()
Returns the hash code for thisExpression
.boolean
isLiteralText()
Returns whether this expression was created from only literal text.boolean
isReadOnly(ELContext context)
Evaluates the expression relative to the provided context, and returnstrue
if a call toValueExpression.setValue(javax.el.ELContext, java.lang.Object)
will always fail.void
readExternal(java.io.ObjectInput in)
void
setValue(ELContext context, java.lang.Object value)
Evaluates the expression relative to the provided context, and sets the result to the provided value.java.lang.String
toString()
void
writeExternal(java.io.ObjectOutput out)
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Field Detail
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expectedType
private java.lang.Class expectedType
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expr
private java.lang.String expr
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fnMapper
private FunctionMapper fnMapper
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varMapper
private VariableMapper varMapper
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node
private transient Node node
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Constructor Detail
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ValueExpressionImpl
public ValueExpressionImpl()
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ValueExpressionImpl
public ValueExpressionImpl(java.lang.String expr, Node node, FunctionMapper fnMapper, VariableMapper varMapper, java.lang.Class expectedType)
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Method Detail
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equals
public boolean equals(java.lang.Object obj)
Description copied from class:Expression
Determines whether the specified object is equal to thisExpression
.The result is
true
if and only if the argument is notnull
, is anExpression
object that is the of the same type (ValueExpression
orMethodExpression
), and has an identical parsed representation.Note that two expressions can be equal if their expression Strings are different. For example,
${fn1:foo()}
and${fn2:foo()}
are equal if their correspondingFunctionMapper
s mappedfn1:foo
andfn2:foo
to the same method.- Specified by:
equals
in classExpression
- Parameters:
obj
- theObject
to test for equality.- Returns:
true
ifobj
equals thisExpression
;false
otherwise.- See Also:
Hashtable
,Object.equals(java.lang.Object)
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getExpectedType
public java.lang.Class getExpectedType()
Description copied from class:ValueExpression
Returns the type the result of the expression will be coerced to after evaluation.- Specified by:
getExpectedType
in classValueExpression
- Returns:
- the
expectedType
passed to theExpressionFactory.createValueExpression
method that created thisValueExpression
.
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getExpressionString
public java.lang.String getExpressionString()
Returns the type the result of the expression will be coerced to after evaluation.- Specified by:
getExpressionString
in classExpression
- Returns:
- the
expectedType
passed to theExpressionFactory.createValueExpression
method that created thisValueExpression
. - See Also:
Expression.getExpressionString()
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getNode
private Node getNode() throws ELException
- Returns:
- The Node for the expression
- Throws:
ELException
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getType
public java.lang.Class getType(ELContext context) throws PropertyNotFoundException, ELException
Description copied from class:ValueExpression
Evaluates the expression relative to the provided context, and returns the most general type that is acceptable for an object to be passed as thevalue
parameter in a future call to theValueExpression.setValue(javax.el.ELContext, java.lang.Object)
method.This is not always the same as
getValue().getClass()
. For example, in the case of an expression that references an array element, thegetType
method will return the element type of the array, which might be a superclass of the type of the actual element that is currently in the specified array element.- Specified by:
getType
in classValueExpression
- Parameters:
context
- The context of this evaluation.- Returns:
- the most general acceptable type; otherwise undefined.
- Throws:
PropertyNotFoundException
- if one of the property resolutions failed because a specified variable or property does not exist or is not readable.ELException
- if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.
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getValueReference
public ValueReference getValueReference(ELContext context) throws PropertyNotFoundException, ELException
Description copied from class:ValueExpression
Returns aValueReference
for this expression instance.- Overrides:
getValueReference
in classValueExpression
- Parameters:
context
- the context of this evaluation- Returns:
- the
ValueReference
for thisValueExpression
, ornull
if thisValueExpression
is not a reference to a base (null or non-null) and a property. If the base is null, and the property is a EL variable, return theValueReference
for theValueExpression
associated with this EL variable. - Throws:
PropertyNotFoundException
ELException
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getValue
public java.lang.Object getValue(ELContext context) throws PropertyNotFoundException, ELException
Description copied from class:ValueExpression
Evaluates the expression relative to the provided context, and returns the resulting value.The resulting value is automatically coerced to the type returned by
getExpectedType()
, which was provided to theExpressionFactory
when this expression was created.- Specified by:
getValue
in classValueExpression
- Parameters:
context
- The context of this evaluation.- Returns:
- The result of the expression evaluation.
- Throws:
PropertyNotFoundException
- if one of the property resolutions failed because a specified variable or property does not exist or is not readable.ELException
- if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.
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hashCode
public int hashCode()
Description copied from class:Expression
Returns the hash code for thisExpression
.See the note in the
Expression.equals(java.lang.Object)
method on how two expressions can be equal if their expression Strings are different. Recall that if two objects are equal according to theequals(Object)
method, then calling thehashCode
method on each of the two objects must produce the same integer result. Implementations must take special note and implementhashCode
correctly.- Specified by:
hashCode
in classExpression
- Returns:
- The hash code for this
Expression
. - See Also:
Expression.equals(java.lang.Object)
,Hashtable
,Object.hashCode()
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isLiteralText
public boolean isLiteralText()
Description copied from class:Expression
Returns whether this expression was created from only literal text.This method must return
true
if and only if the expression string this expression was created from contained no unescaped EL delimeters (${...}
or#{...}
).- Specified by:
isLiteralText
in classExpression
- Returns:
true
if this expression was created from only literal text;false
otherwise.
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isReadOnly
public boolean isReadOnly(ELContext context) throws PropertyNotFoundException, ELException
Description copied from class:ValueExpression
Evaluates the expression relative to the provided context, and returnstrue
if a call toValueExpression.setValue(javax.el.ELContext, java.lang.Object)
will always fail.- Specified by:
isReadOnly
in classValueExpression
- Parameters:
context
- The context of this evaluation.- Returns:
true
if the expression is read-only orfalse
if not.- Throws:
PropertyNotFoundException
- if one of the property resolutions failed because a specified variable or property does not exist or is not readable.ELException
- if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available. * @throws NullPointerException if context isnull
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readExternal
public void readExternal(java.io.ObjectInput in) throws java.io.IOException, java.lang.ClassNotFoundException
- Specified by:
readExternal
in interfacejava.io.Externalizable
- Throws:
java.io.IOException
java.lang.ClassNotFoundException
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setValue
public void setValue(ELContext context, java.lang.Object value) throws PropertyNotFoundException, PropertyNotWritableException, ELException
Description copied from class:ValueExpression
Evaluates the expression relative to the provided context, and sets the result to the provided value.- Specified by:
setValue
in classValueExpression
- Parameters:
context
- The context of this evaluation.value
- The new value to be set.- Throws:
PropertyNotFoundException
- if one of the property resolutions failed because a specified variable or property does not exist or is not readable.PropertyNotWritableException
- if the final variable or property resolution failed because the specified variable or property is not writable.ELException
- if an exception was thrown while attempting to set the property or variable. The thrown exception must be included as the cause property of this exception, if available.
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writeExternal
public void writeExternal(java.io.ObjectOutput out) throws java.io.IOException
- Specified by:
writeExternal
in interfacejava.io.Externalizable
- Throws:
java.io.IOException
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.lang.Object
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